Failure investigations of a first stage Ni based super alloy gas turbine blade

2016-10-25_17h11_11A paper presented at the « International Conference on Processing of Materials, Mineral and Energy », 29th and 30th july 2016, PACE Institute of Technology & Sciences, India. It had been published by Elsevier.

This paper deals with the failure investigations of the first stage gas turbine blade of 30MW gas turbine. This blade is manufacture with of nickel based super alloy IN738. The main focus of the paper is to found the causes of failure of the blade. By the investigations, it is found that the blade failure takes place due to the combined effect of erosion, oxidation, overheating, and hot corrosion.

More at : http://www.pmme.co.in/papers/EMT-087.pdf

Comparative study of Fatigue Analysis of Pop up (Blind) Riveted with Solid Riveted Lap joint

2016-10-25_16h45_34An article published in the « International Journal of Engineering Science and Computing », June 2016.

This paper study failure observed in riveted joint in buses and give solution to overcome this failure. In this stress analysis, fatigue analysis of pop up (Blind) riveted joint and Solid riveted lap joints are studied and from that predict the maximum shear strength of riveted joint to resist shear failure and no. of cycles of riveted joints. Also study the behavior of stresses and fracture observed on the Riveted due to stresses. This study is done by CAD software CATIA V5, CAE software Abaqus and correlate with analytical solution.

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Mechanics of Collapse of WTC Towers

A telechargementpaper published in september 2016 on www.civil.northwestern.edu .

Abstract : The previously formulated model of the gravity-driven collapse of the twin towers of the World Trade Center on 9/11/2001 was shown to match all the existing observations, including the video record of the crush-down motion of the top part of tower during the first few seconds, the seismically recorded duration of collapse, the size distribution of particles caused by impact comminution of concrete floor slabs, the loud booms due to near-sonic lateral ejection velocity of air and dust, and precedence of the crush-down collapse mode before the crush-up. Nevertheless, di↵erent degrees of ductility, fracturing and end support flexibility of WTC columns could lead to an equally good match of these observations and remained uncertain, due to lack of test data. Recently, Korol and Sivakumaran reported valuable experiments that allow clarifying this uncertainty. They reveal that, under the assumptions of rigid end supports and unlimited ductility (or no fracturing), the energy dissipation in the WTC columns would have been at maximum 3.5-times as large as that calculated by the plastic hinge mechanism normally considered for small deflection buckling. This increase would still allow close match of all the aforementioned observations except for the first two seconds of the video. The proper conclusion from Korol and Sivakumaran’s tests, based on close matching of the video record, is that the fracturing of columns and the flexibility of end restraints must have significantly reduced the energy dissipation in columns calculated under the assumptions of no fracture and no end restraint flexibility.

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Stress corrosion cracking of full sized rockbolts

2016-06-04_07h48_16An article published in  « International Journal of Rock Mechanics & Mining Sciences – 81 (2016)« .

Previous studies had identified that a testing protocol was required to examine stress corrosion cracking (SCC) of full sized rockbolts under simulated in situ conditions. It was found that SSR testing provided an appropriate analogue for examining rockbolt susceptibility to SCC and was thus used to examine the effect of grit blasting, galvanising and varying steel grades on the SCC resilience of rockbolts. Of these, 300 grade steel and galvanising provided the most promising resistance to SSC, while grit blasting provided a 40% improvement in resistance compared to untreated HSAC 840 grade rockbolts.

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Failure investigations of a 900 KV bil trench cota bushing

A case study of failure discussed in the 82 nd International Conference of Doble Clients.

bushingThe discussion of this paper will focus on the H1 Trench COTA bushing, which failed after field maintenance handling that would not normally be expected to have a negative effect on a bushing. Following the failure, the top air side porcelain was found ruptured and missing; the bottom insulator was fractured into a number of pieces. The H2 and H3 bushings from this transformer, which were identical Trench type bushings, were also removed and disassembled for inspection to help identify a possible root cause of the H1 bushing failure.

More at : http://www.doble.com/content/show/boston2015/files/BIIT/BIIT-2_Trench_COTA_Failure_Root_Cause_Mani.pdf

 

Fatigue Failure of Aluminium Alloy Piston

An article published in International Research Journal of Engineering and Technology (IRJET), Volume: 03 Issue: 04 | Apr-2016.
pistonAn analytical study was performed about piston failure by fatigue. Fatigue cracks are initiated and propagated by the action of mechanical and high temperature loading conditions which induces cyclic stresses in the piston material.  Various proposals and solutions are presented so that necessary care can be taken to prevent piston failure in future.

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Failure Analysis of a Reactor after Explosion Accident

2016-04-18_23h00_19A paper published in « Procedia Engineering« , Volume 130, 2015.

Burst of a reactor occurred in an explosion accident during the production of antistatic agent process. According to the results of site survey, the current regulations and standards as well as the requirements of the accident investigation group, the reason of burst was discussed by failure analysis of the shell and bolts.

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Cas Concrets – Quatre défaillances par fissuration progressive

Avatar Cas ConcretsQuatre cas d’analyses de défaillances survenues en service : un vilebrequin de moteur marin, un arbre épaulé, un maillon de chaine d’élévateur et un taillant de forage. Ces quatre fiches d’analyse de défaillance avaient été publiées entre 1984 et 1985 dans la revue Cetim-information. Des dizaines de milliers de cas ont été traités ces quarante dernières années par le Cetim. Cette expérience fait du Centre une référence dans le domaine à même d’intervenir dans tous les secteurs d’activités. Avec aujourd’hui ses centres associés et partenaires, l’Institut technologique Cetim met un ensemble de compétences et de moyens au service des industriels et experts pour analyser, comprendre et proposer des solutions permettant d’éviter la reproduction de ces défaillances. Les différentes expertises de cette série « Cas concrets » sont issues d’articles publiés dans la revue Cetim Informations dans les années 74 à 90. Bien que ces fiches traitant de cas concrets soient anciennes, leur contenu est toujours d’actualité…

Source : Cas Concrets – Quatre défaillances par fissuration progressive – Cetim – Centre technique des industries mécaniques

Quand le BEA s’appuie sur les compétences du Cetim

2016-03-10_08h41_34Erreur humaine ou défaillance technique ? Suite à un accident d’hélicoptère, le Bureau d’enquêtes et d’analyses (BEA) a fait appel à l’expertise du Cetim dans les matériaux composites. Sa mission : étudier les débris de la poutre de queue de l’appareil, afin de déterminer les causes exactes du sinistre. Découvrez en image cette enquête de haut vol sur notre site.

Pour en savoir plus, retrouvez les experts du Cetim sur le salon JEC World Composite Show & Conferences, du 8 au 10 Mars 2016 à Paris Nord Villepinte, Espace régional Pays de la Loire, stand 6P57. Vous pouvez également consulter le site du Cetim, rubrique « Agenda ».

Deux conduites forcées sur écoute

EDF-Tignes-Malgovert_Img_DetailReference

 

EDF a mis sous surveillance par émission acoustique les conduites forcées de la centrale de Malgovert. Objectif : détecter en temps réel, pendant deux années et demie, la rupture de frettes en acier à haute limite élastique.

 

Pour cela, Le Cetim a développé en 2011 un système basé sur le principe de l’émission acoustique. Des tests de propagation d’ondes ont d’abord été menés sur site afin de rechercher les capteurs les mieux adaptés tout en optimisant leur nombre. La simulation des ruptures de frettes sur site a ensuite permis de s’assurer de l’efficacité des capteurs à moyenne fréquence (100 kHz) pour détecter les défauts. Le bruit de fond dû à la circulation de l’eau dans les conduites a également été analysé.

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